Trump's political rise shows that a top concern for many Americans is that immigrants take jobs and depress the wages of similarly skilled, native workers. Immigration economist George Borjas at the Harvard Kennedy School has analyzed how much immigration can lower the wage of competing workers. A 10 percent increase in worker supply can reduce wages by 3 percent to 4 percent, according to his influential research.
But the debate goes beyond wages. Research conducted by William Olney, associate professor of economics at Williams College, has found the availability of more low-skilled workers can prompt existing U.S. businesses to expand operations. Immigration also increases the number of small businesses in mobile, low-skilled intensive industries, such as manufacturing, wholesale trade and transportation and warehousing.
Total immigrants, both legal and unauthorized, comprise roughly 17 percent, or more than 26 million, of the civilian U.S. workforce.
"It's very difficult to imagine the economy functioning without this workforce, which has grown so large over a long period of time," said Pia Orrenius, senior economist at the Federal Reserve Bank of Dallas.
Fewer immigrants could mean lowered rates of U.S. productivity, less innovation and fewer small businesses that are created.
"It would create enormous problems that economists would call a recession," Kehoe said.